Package jmri.jmrix.dcc4pc

Class Dcc4PcRawDecoder

java.lang.Object

jmri.jmrix.dcc4pc.Dcc4PcRawDecoder

public class Dcc4PcRawDecoder
extends Object

Decodes the Raw RailCom encoding of a DCC4PC RailCom reader (Omnibus specification section 9.3). Each packet gives one DCC packet the reader saw, the state of every enabled input and the RailCom bytes each input with RailCom data received in the cutout that followed.

The encoding is stateful: type 1 packets carry no input states and inherit them from the packet before, and the number of duplicate-flag and length bytes that follow depends on those states. RailCom data may also be sent as "duplicate of the 1st, 2nd or 3rd previous" for an input. The decoder therefore only works on an unbroken stream that starts right after a Reset Encoding State, which sets every input to unoccupied. A Get Data reply may end part way through a packet; the leftover bytes are kept and joined to the next reply.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	Dcc4PcRawDecoder.InputData	RailCom bytes for one input.
static enum	Dcc4PcRawDecoder.Kind
static class	Dcc4PcRawDecoder.Packet	One decoded packet.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	OVERFLOW	The reader's output buffer overflowed and packets were lost here.
static final int	STATE_OCCUPIED
static final int	STATE_ORIENTATION_A
static final int	STATE_ORIENTATION_B
static final int	STATE_UNOCCUPIED

Constructor Summary

Constructors

Constructor	Description
Dcc4PcRawDecoder(int[] enabledInputs)

Method Summary

Modifier and Type	Method	Description
List<Dcc4PcRawDecoder.Packet>	decode(int[] chunk)	Decode a chunk of Get Data reply bytes.
int[]	getInputs()
void	reset()	Start again as the reader does after a Reset Encoding State: every input unoccupied, no partial packet and no RailCom history.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

STATE_UNOCCUPIED

public static final int STATE_UNOCCUPIED

See Also:

• Constant Field Values

STATE_OCCUPIED

public static final int STATE_OCCUPIED

See Also:

• Constant Field Values

STATE_ORIENTATION_A

public static final int STATE_ORIENTATION_A

See Also:

• Constant Field Values

STATE_ORIENTATION_B

public static final int STATE_ORIENTATION_B

See Also:

• Constant Field Values

OVERFLOW

public static final int OVERFLOW

The reader's output buffer overflowed and packets were lost here.

See Also:

• Constant Field Values

Constructor Details

Dcc4PcRawDecoder

public Dcc4PcRawDecoder(int[] enabledInputs)

Parameters:

enabledInputs - the inputs enabled on the reader, numbered from 1, in ascending order

Method Details

getInputs

public int[] getInputs()

Returns:

the enabled inputs, numbered from 1, in the order their states are reported

reset

public void reset()

Start again as the reader does after a Reset Encoding State: every input unoccupied, no partial packet and no RailCom history.

decode

public List<Dcc4PcRawDecoder.Packet> decode(int[] chunk)

Decode a chunk of Get Data reply bytes.

Parameters:

chunk - the reply bytes, each 0-255

Returns:

every packet completed by this chunk